Publications

3530

Endosymbionts play crucial roles in various physiological activities within insect hosts. The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is an important vector for Candidatus Liberibacter asiaticus (CLas), a fatal pathogenic bacterial agent causing the disease Huanglongbing in the citrus industry. This study combines high-throughput sequencing of 16S ribosomal RNA amplicons to explore how CLas affects the bacterial community in different color morphs (blue, gray), genders, and tissues (cuticle, gut, mycetome, Malpighian tubule, ovary, and testis) of ACP. We found that there was no significant differences in the bacterial community diversity and CLas acquired ratio between the different color morphs and genders of ACP adults. However, acquiring CLas could promote the adult bacterial community’s diversity and richness more than in the uninfected condition. The presence of CLas could increase the Wolbachia and unclassified_Enterobacteriaceae proportions more than in the uninfected condition. The bacterial community diversity in the CLas infected tissues of ovary and cuticle, was lower than the uninfected condition, but the richness of all tissues was not different between the infected and uninfected conditions. CLas could also change the bacterial structure in different tissues and make the bacterial relationship network simpler than it is in an uninfected condition. Furthermore, we used quantitative real-time PCR to assess the dynamic changes of Wolbachia in CLas uninfected and infected color morphs and tissues of ACP. The results showed that Wolbachia titers were significantly higher in CLas infected adults than in uninfected adults. In different tissues, the Wolbachia titers in the testis, ovary, and Malpighian tubule were higher than their uninfected counterparts. Our results provide essential knowledge for understanding the symbionts of the ACP and how CLas affects the bacterial community of the ACP.

Huanglongbing (HLB), referred to as citrus greening disease, is a bacterial disease impacting citrus production worldwide and is fatal to young trees and mature trees of certain varieties. In some areas, the disease is devastating the citrus industry. A successful solution to HLB will be measured in economics: citrus growers need treatments that improve tree health, fruit production, and most importantly, economic yield. The profitability of citrus groves is the ultimate metric that truly matters when searching for solutions to HLB. Scientific approaches used in the laboratory, greenhouse, or field trials are critical to the discovery of those solutions and to estimate the likelihood of success of a treatment aimed at commercialization. Researchers and the citrus industry use a number of proxy evaluations of potential HLB solutions; understanding the strengths and limitations of each assay, as well as how best to compare different assays, is critical for decision-making to advance therapies into field trials and commercialization. This perspective aims to help the reader compare and understand the limitations of different proxy evaluation systems based on the treatment and evaluation under consideration. The researcher must determine the suitability of one or more of these metrics to identify treatments and predict the usefulness of these treatments in having an eventual impact on citrus production and HLB mitigation. As therapies advance to field trials in the next few years, a reevaluation of these metrics will be useful to guide future research efforts on strategies to mitigate HLB and vascular bacterial pathogens in other perennial crops.

Abstract Anaerobic ammon ium oxidizing (anammox) bacteria oxidize ammonium and reduce nitrite, producing N2, and could play a major role in energy-optimized wastewater treatment. However, sensitivity to various environmental conditions and slow growth currently hinder their wide application. Here, we attempted to determine online the effect of environmental stresses on anammox bacteria by using an overnight batch activity test with whole cells, in which anammox activity was calculated by quantifying N2 production via headspace-pressure monitoring. A planktonic mixed culture dominated by “Candidatus Kuenenia stuttgartiensis” strain CSTR1 was cultivated in a 30-L semi-continuous stirring tank reactor. In overnight resting-cell anammox activity tests, oxygen caused strong inhibition of anammox activity, which was reversed by sodium sulfite (30 µM). The tested antibiotics sulfamethoxazole, kanamycin, and ciprofloxacin elicited their effect on a dose-dependent manner; however, strain CSTR1 was highly resistant to sulfamethoxazole. Anammox activity was improved by activated carbon and Fe2O3. Protein expression analysis from resting cells after anammox activity stimulation revealed that NapC/NirT family cytochrome c (KsCSTR_12840), hydrazine synthase, hydrazine dehydrogenase, hydroxylamine oxidase, and nitrate:nitrite oxidoreductase were upregulated, while a putative hydroxylamine oxidoreductase HAO (KsCSTR_49490) was downregulated. These findings contribute to the growing knowledge on anammox bacteria physiology, eventually leading to the control of anammox bacteria growth and activity in real-world application. Key Points • Sulfite additions can reverse oxygen inhibition of the anammox process • Anammox activity was improved by activated carbon and ferric oxide • Sulfamethoxazole marginally affected anammox activity Graphical abstract

Intestinal microbiota has been involved in several processes that benefit the host, such as digestion, nutrient metabolism, resistance to pathogens colonization and immune function. In this study, we investigated the diversity, composition and functional prediction of microbiota of reared Seriolella violacea (palm ruff) in the same cohort sampled at different times (7-, 8- and 9-month-old). Microbial community structure analyses, using 16S rRNA amplicon sequencing, revealed that the intestinal microbiota was dominated by the phyla Firmicutes, Proteobacteria, Fusobacteria and Tenericutes. At the genus level, Candidatus Arthromitus was the most abundant in all sampled timepoints, representing in average 78% of the bacterial community (ranging from 18 to 98%), corresponding to segmented filamentous bacteria, which are interesting because they have been associated with the maturation of immune responses in the gut and protecting the host from bacterial infections. The comparisons of the intestinal microbiota among the three groups showed differences in abundance of bacterial taxa and also in alpha diversity indexes (Shannon and Simpson), as well as beta diversity metrics (weighted and unweighted UniFrac). Potential functions of the intestinal microbiota of palm ruff were retrieved using Philipin and Tax4fun and these analyses revealed high levels of genes for sugar metabolism. To our knowledge, this study represents the first description of the intestinal microbiota of S. violacea.